Whenever a communications device, in the following denoted user equipment (UE), is connected to a communications network for obtaining a service, such as a data session or a voice session, the user of the device expects continued service without interruption. If the service is frequently disconnected, it would lead to a poor user perception and dissatisfaction, which will also affect the operator revenues.
Hence acknowledging the importance of retaining a call, there are various methodologies to improve the retainability in the communications network. One such methodology is network assisted re-establishment of connections. Whenever a failure occurs in the radio connection, the UE may attempt to re-establish the existing connection rather than starting from the beginning. Such re-establishment improves the user perception and leads to a much smaller interruption time than if starting up a connection again. This procedure is, in Long Term Evolution (LTE), called Radio Resource Control (RRC) Connection Re-Establishment.
There are various reasons to a failure in the connection, for instance poor performance for the UE in a currently serving cell or some sudden occurrence, such as a reconfiguration failure. In either case, the UE can perform a RRC Connection Re-establishment in order to recover the connection either to the same cell or, after selecting a suitable target cell, to the target cell. Whenever this re-establishment is carried out and the connection is continued in a cell provided by a target node other than the currently serving node (also denoted source node), the target node needs to obtain the previous information related to the call in order for the connection to indeed be continued.
The initial inputs needed to transfer this information from the source node to the target cell, is provided by the UE. Upon successfully obtaining all the required information, the RRC Connection is re-established and the call (or other service) is continued. Hence, for the call to be re-established in this case, i.e. when the target cell is provided by another node than the serving cell, it is necessary for the UE to provide sufficient information in the uplink and any missing information may lead to failure in the execution.
The current re-establishment methodology also relies on the serving node and the target node exchanging information. This information exchange is however not always possible, e.g. due to inter-vendor issues, and the RRC re-establishment will then not be successful.